Spike perked up as an alarm went off. "Intruder alert! A spy is in the base! Protect the prisoner!"
"Yo! A little help here?!" he heard a voice yell outside the door of the room he was being kept in. Mouth muzzled and tied up with a lot of rope and duct tape.
"Alright I got it. Stand back, son," another voice said. "One, one, one, uh... one." The sound of the door unlocking could be heard over the alarm. That was the door code? Pretty weak in Spike's opinion.
"Let's go! Let's go!" the first voice said frantically.
"INCOMING!!!" a third voice bellowed before the door was knocked off its hinges, letting a group of three ponies, two earth ponies and a pegasus, into the room, ready to shoot.
"Hey he's still here!" the pegasus said.
"Alright then," the machine gun toting earth pony said.
"Ahem!" Their attention was drawn to the door, where a changeling was holding a dead body. "Gentlecolts." He started walking toward them. "I see the prisoner is safe. Tell me. Did any of you kill the enemy spy on your way here?" After they were silent for a moment, he spoke again. "No? Then we still have a problem," he said as he deposited the body he was carrying on the table, showing the butterfly knife lodged at the base of the unicorn's skull.
"And a knife," the shotgun wielding pony said.
"Ooh! Big problem! I've killed plenty of spies," The pegasus said as he pulled the knife out and started twirling it. "They're bit a dozen, backstabbing scumbags. Like you, Ow!" he dropped the knife as the blade nicked him. "No offense."
"The changeling picked up the knife. "If you managed to kill them, I assure you they were not like me," he said as he closed the knife in a flourish and handed it to the pegasus. "And nothing, nothing like the mare loose inside this building."
"What are you, president of her fanclub?" the pegasus asked, getting laughs from the two earth ponies.
"No," the changeling said easily. "That would be our prisoner," he said as he threw down a folder that spilled out photos of Spike and Rarity in the throes of passionate lovemaking, getting some wolf whistles from the ponies. And causing Spike to blush under his muzzle. "And now she's here to fuck us. So listen up, boy! Or those photos will be the last pleasant sight you'll ever see," he said as he lit a cigarette and took a drag. "This spy has already breached our defenses."
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Rarity made her way to the end of a hallway and sighted a lone engineer tending his sentry gun. Prepping a sapper, she quickly made her way over and slid the sapper under the sentry to take it out as she pulled a revolver and shot the engineer between the eyes point blank.
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"You've seen what she's done to our colleagues," the changeling said.
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A sniper turned and tried to point his rifle at Rarity, only for her to disarm him and kick him into the boards over the window, breaking them. The sniper grabbed his knife and tried to slash Rarity. But the fashionista easily parried and stabbed the base of his skull, letting him fall down a stairwell.
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"And worst of all: she could be any one of us," the changeling said.
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Rarity pinned a medic and assumed his form with a spell before snapping his neck and hiding the body before walking away.
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"She could be in this very room!" the changeling said. "It could be you!" he said as he pointed at the machine gunner. "It could be me! It could even be - " he was cut off by his head getting blown off.
"WHOA WHOA WHOA!!!" the pegasus yelled.
"What?! It was obvious!" the shotgun user said as he chambered a new round. "He's the one. Watch. He'll change back any second now." They all waited, and his confidence started waning when nothing happened. "Annny second now."
"So... we've still got a problem," the machine gunner said as the pegasus started moving toward them while they were distracted by the changeling's body, the knife held in a blue magic aura.
"Big problem," the shotgun user said as the knife silently opened. "Alright. Who's ready to go find this spy?" He never saw the smirk that appeared on Spike's face as the pegasus dropped his disguise to reveal Rarity.
"Right behind you," Rarity said. The oh crap faces of the two earth ponies was priceless to Spike as he watched Rarity stab them to death before they could react. Smiling sweetly, Rarity went over to Spike and cut him free while her telekinesis removed his muzzle. "Ah... My dear Spiky Wikey," she said as she nuzzled him lovingly. "Let's get out of here."